JUNCTION

Abstract: The present invention is related to a joint structure for sandwich panels comprised of a mineral wool core (1) which is advantageously clad on both sides by skin sheets (2) bonded to the mineral wool core. The mineral wool core (1) is left bare on the edge remaining between a groove-and-tongue structure (3, 3') included in the skin sheet structure to accomplish the mating of the surfaces of the mineral wool core of the panels to be jointed. To assure the tightness of the joint, the mineral wool core (1) is at the area of the tongue-and-groove joint subjected to a higher compressive contraction in the mating direction of the panels than elsewhere in the core after the skin sheet structures of the panels are pushed home in their tongue-and-groove joints.

Description: J U N C T I O N The present invention relates to a joint structure for structural sandwich panels comprised of a mineral wool core clad on both wide faces by skin sheets. The skin sheets in such panels known in the art are conventionally made from sheet metal bonded to the mineral wool core. The core is made from so-called structural mineral wool having an essential integral strength. The shear strength of the core material is in the order of 25 - 100 kN/cm 2 . The core and the skin sheet are bonded together using an adhesive. The edges of the panels are fabricated into a tongue-and- groove structure formed from the skin sheets thus facili- tating the jointing of the panels. To assure the integrity of thermal insulation over such a joint, the mineral wool core is left unclad at the panel edges over at least a portion of the edge surface remaining between the tongue- and-groove members formed by the skin sheets . The tongue-and-groove structures and the mineral wool core are dimensioned so that when the panels are ready mounted in place using the tongue-and-groove locking, the unclad edges of the mineral wool core remain resting against each other. Such an integrity of the joint is extremely important not only for the sake of thermal insulation, but also in a crucial manner to counteract fire spreading. The mineral wool core of the panel is extremely fire-resistant, but due to contraction or movement of the mineral wool, crevices may appear in the joint structure that deteriorate the fire resistance performance. To make the core sections of the panels to be jointed mate tightly with each other, extremely tight manufacturing tolerances must be applied. Furthermore, the fixing of the panels to each other has in the prior art been implemented with the help of various fixture elements such as screws to prevent the movements of the panels relative to each other from compromising the integrity of the joint. An example of such a joint structure can be found in EP patent applica¬ tion A 0,289, 096. It is an object of the joint structure according to the invention to achieve a joint having a resilient allowance with respect to the dimensioning and small mutual movements of the panels without compromising thermal insulation and fire resistance properties. It is a further object of the joint structure according to the invention to facilitate the fixing of the panels to each other without the use of screws or other separate fixture elements that affect the appearance and ease-of-use of the panels and increase their mounting costs. The advantageous goals defined above are attained according to the invention by severing the bonding strength from the initially tight bond of said edge to the skin structure over at least a portion of at least one of the unclad edges of the cores to be mated and for a depth at least essen¬ tially equal to half the height of the tongue-and-groove joint structure. By nature, mineral wool has a somewhat resilient structure. However, the structural mineral wool used as the core of a panel has a high compressive strength. As the wool is also conventionally adhesively bonded to the skin up to the edge of the tongue-and-groove structure, inward compression of the mineral wool core during the panel mounting step neces¬ sitates to overcome, not only the compressive strength of the wool, but also the shear strength of the bond to the skin, which has prevented the utilization of the resilience of the mineral wool in prior-art joint structures. According to the basic concept of the invention, the core is made compressible at the joint area by providing the mineral wool forming the panel core with a possibility of undergoing contraction under compression over the entire area of the mating surfaces in the joint. According to a specific embodiment of this concept, the mating area in the joint is provided with a separate sealer strip of more resilient (softer) mineral wool than that used in the panel core proper. The resilience of the mineral wool core at the joint also facilitates new kinds of joint structures between the skin sheets by virtue of locking notches/tabs cut in the tongue- and-groove edges of the skin sheets . In an embodiment of the invention in which the panel core proper is provided with an improved compressibility over that feasible in a conventional panel, the panel core is fabricated slightly overextending at the edges. The joint edge of the panel core is then severed to include cuts or furrows extending toward the interior of the panel core and running parallel with the joint edge of the panel. The pur¬ pose of such cuts or furrows is to reduce the compressive strength imparted by the bonding of the core to the skins and thus to give the panel core a greater compressive resilience at its joint edge freed from the counteracting effect of shear forces to the compression. Simultaneously, the cuts made as narrow furrows provide the mineral wool with more space for compression. When the depth of the tongue-and-groove joint between the panels is approx. 15 - 20 mm, the cuts or furrows can be made approx. 15 - 50 mm deep depending on the wool type. The cuts or furrows can be made only on one of the mating edges, or alternatively, on both. If the cuts or furrows are made on both of the mating joint edges, their depth can be smaller than when they are made on the edge of only one of the mating panels . In an embodiment of the invention in which a different type of mineral wool is used as a strip in the joint, the mineral wool core of the panel must be left slightly undersized. Fabrication of the core to an undersize can be attained by, e.g. , cutting a strip off from the cores of both mating panels, or alternatively, only from the core of one of the panels . The entire depth of the strip thus removed, either from one panel or from both, must be essen¬ tially equal to the depth of the tongue-and-groove joint. The gap thus formed is filled, advantageously slightly overfilled, with a mineral wool strip of advantageously higher compressibility than that of the mineral wool used in the core panel proper. The invention is next examined in greater detail with reference to the appended drawing illustrating the joint structure, plus as an integral part of thereof, mutual locking arrangements for the facing sheets, in which drawing: Figure 1 is a cross-sectional view of the mating edges of two panels to be joined, said edges including two alternative structural details fabricated according to the invention; Figure 2 is a perspective view of an embodiment of a mutual locking arrangement for the side sheets of two panels to be joined; Figure 3 is a perspective view of an alternative embodi¬ ment of a locking arrangement for the same purpose; Figure 4 is a perspective view of a further alternative embodiment of a locking arrangement for locking the skin sheets to each other; Figure 5 is a perspective view of further another alter¬ native embodiment of a locking arrangement for locking the skin sheets to each other; and Figure 6 is a cross-sectional view of an alternative embodiment of the joint structure according to the invention shown in the diagram of Fig. 1. With reference to Fig. 1, the lower edge and upper edge of two conventional sandwich panel structures are shown, both edges having been contoured for a mating joint. The panels comprise a core 1 made from a mineral wool board and clad on both sides by a skin sheet 2. The skin sheets are bonded to the core using an adhesive. At the area of the panel edges, the skin sheets are shaped into conventional tongue- and-groove structures 3, 3 ' . The panel edges are left unclad at the area used for the tongue-and-groove joint so that the mineral wool core surface remains bare. When the panels are abuttingly mounted in place, said bare surfaces of the mineral wool core 1 advantageously mate with each other in a slightly compressed state. As shown in Fig. 1, the mineral wool core 1 in the joint edge of the lower panel is severed by cuts 4 made extending from the surface of the bare core toward the interior of the panel core and running parallel with the joint edge of the panel. The purpose of such cuts is to detach that part of the mineral wool core remaining between the cuts from that part of the mineral wool core which is tightly bonded to the skin sheets 2. In this manner the skin structure of the panel is disconnected from the compressible core, whereby it cannot any more counteract the compression of the mineral wool core proper. Said cuts can be to a depth of approx. 20 - 50 mm deep, either to one or both of the edges of the panels to be jointed. In lieu of slit-like cuts shown in the diagram, the cuts 4 made in the mineral wool core can also be implemented as narrow furrows which provide the mineral wool in the core with more space for compression. Another alternative for achieving a resilient joint is shown for the upper panel illustrated in the diagram, where a strip which is cut off from the mineral wool core at the panel lower edge is replaced by separate sealer strip of mineral wool. If such a strip is of a mineral wool type of higher compressibility than that used in the panel core, the strip facilitates a resilient compressibility of the joint better than that achievable by merely juxtaposing the panel cores as such. With reference to the embodiment shown in Fig. 6, the cuts made in the mineral wool core 1 are fabricated as narrow furrows 5 and 6, which are aligned obliquely into the mineral wool core 1 at an angle relative to the plane of the panel. Such furrows can be aligned from the joint surface obliquely either toward the center plane of the panel core, or alternatively, toward the panel surface. Said slit-like cuts 4 or furrows 5, 6, 6' can be made in a greater number staged in the thickness direction of the panel, however, without compromising the required total strength of the joint structure. The cuts and furrows may be made with different orientation angles and/or depths relative to each other. A useful joint structure is also achievable by virtue of working the initially cohesive structure of the mineral wool comprising the core so as to impart the wool greater flexibility and easier compressibility. Such a working must be done by weakening the mutual binding of the mineral fibers. A proper working method is, e.g., sufficiently vigorous compression of the mineral wool over the entire length of the joint edge using, e.g., a reciprocating press roll apparatus. This kind of a working process detaches the mutual adherence of the fibers bonded with a binder, thus resulting in greater fluffiness of the mineral wool. Simultaneously, the volume of the worked wool increases, thus providing a suitable sealer strip of resilient wool for the joint. This working method can be applied to both joint edges included the above-described separating cuts and joint edges without such separating cuts. The above-described modifications to a joint structure have been found to impart an essential improvement particularly to the fire-resistance of panels, because the modified joint permits larger mutual movements and distortions of the panels without permitting the joints to open. A further enhancement of such an advantageous result can be obtained by virtue of modifications to the skin sheets of the panel. The purpose of such modifications is to achieve greater security in the mutual locking of the panels to each other, whereby in, e.g., fire occasions their mutual movement relative to each other is limited to a smaller scale than is possible by means of a conventional joint structure. With reference to Fig. 2, an embodiment of a locking arrangement of the skin sheets is shown which is particu¬ larly advantageously suited for use in the present joint structure. At the upper edge of the panel, and at its lower edge, respectively, the skin sheets 2, 2' are bent to form a tongue-and-groove joint comprising flanges 2a, 2b, which protrude orthogonally outward from the plane of the panel and are shaped to mate tightly parallel with each other when the panels are abuttingly mounted in place. Each of the flanges is fabricated to include locking notches 5, 5' . The notch 5 in the flange 2a at the upper edge of the panel is made by either entirely removing the flange material at the notch, or alternatively, slitting the sheet material (Fig. 3, ref . numeral 5'") - Correspondingly, the flange 2b at the lower edge of the panel is worked so that a part of the material cut free at the notch 5 ' is bent along the base line of the notch inward to form a catch claw 5" . Particularly owing to the resilient joint structure accord- ing to the invention, this claw can during the mounting of the panels be pressed to slide under the bottom edge of the notch 5 in the panel upper edge flange 2a. After the claw 5" has been inserted under the bottom edge of the notch 5 in the lower panel flange 2a, the resilient compression of the mineral wool tends to push the elements slightly apart from each other, whereby the claw 5'' becomes locked to the flange 2a. Such a mutual locking of the skin sheets provides an essen- tial improvement to the mutual locking of the skin sheets in, e.g., a fire occasion, thus limiting the mutual distor- tional or translational movement of the panels relative to each other to a smaller scale than occurs in panels with a conventional joint structure. The mutual locking of the flanges can also be attained using alternative notch/tab embodiments some of which are shown in Figs . 4 and 5. In these embodiments the edges of the notches 5 are made lockable to each other by means of locking tabs partially cut loose from the sheet material at the notch, after which said locking tabs can be brought to lock with each other by moving the panels to be jointed so that they slide relative to each other in the direction of the joint.

Claims: Claims : 1. A joint structure for sandwich elements comprised of a structural mineral wool core (1) clad on both sides by skin sheets (2) bonded to the core, said skin sheets covering the wide faces of the core and extending over a part of the edge surface of the element so as to form at this over- extending area a groove-and-tongue structure (3, 3') which is designed to bring the mating surfaces of the core (1) at their areas unclad by the skin sheet under a compressive load, c h a r a c t e r i z e d in that at least a portion of at least one of the unclad edges of the cores (1) to be mated is detached from its tight bond to the skin structure of the panel for a depth at least essentially equal to half the height of the tongue-and-groove joint structure (3 , 3 ' ) . 2. A joint structure as defined in claim 1, c h a r a c ¬ t e r i z e d in that the tight bond of the mineral wool core to the skin structure of the panel is detached by cuts made in the mineral wool core parallel to the plane of the panel . 3. A joint structure as defined in claim 1, c h a r a c - t e r i z e d in that the tight bond of the mineral wool core to the skin structure of the panel is detached by a cut aligned to an angle relative to the plane of the panel. 4. A joint structure as defined in claim 3, c h a r a c - t e r i z e d in that said cut is aligned from the joint surface obliquely toward the panel surface. 5. A joint structure as defined in claim 3, c h a r a c ¬ t e r i z e d in that said cut is aligned from the joint surface obliquely toward the center plane of the panel core. 6. A joint structure as defined in any of foregoing claims 2 - 5, c h a r a c t e r i z e d in that the mineral wool core is provided with a plurality of cuts performing the function of such a cut that in the thickness direction detaches the tight bond to the skin structure. 7. A joint structure as defined in any of foregoing claims 1 - 6, c h a r a c t e r i z e d in that the tight bond of the mineral wool core to the skin structure is detached by removing material from the core. 8. A joint structure as defined in claim 7, c h a r a c ¬ t e r i z e d in that the mineral wool removed from the „ core is replaced by a mineral wool type of more resilient compressibility. 9. A joint structure as defined in claim 1, 2 or 3 , c h a r a c t e r i z e d in that the tight bond of joint edge area to the skin structure is subjected to a working process which detaches the mutual bonds of the fibers in the mineral wool core (1) . 10. A joint structure as defined in any of foregoing claims 1 - 9, c h a r a c t e r i z e d in that the joint structure for connecting the skin sheets (2, 2') together comprises flanges (2a, 2b) , which protrude orthogonally outward from the plane of the panel and are shaped to mate tightly parallel with each other, and that the flanges are fabricated to include locking notches (5, 5') at predeter- mined spacings from each other, and that at least one of the skin sheets is worked to include a locking tab made by partially cutting it free from the sheet material.

Inventors: HESELIUS LARS-HENRIK, HOLMBERG LARS-PETER, WILLMAN TARMO, HESELIUS, LARS-HENRIK, HOLMBERG, LARS-PETER, WILLMAN, TARMO
Applicants: HESELIUS LARS HENRIK, HOLMBERG LARS PETER, PAROC OY AB, WILLMAN TARMO, HESELIUS, LARS-HENRIK, HOLMBERG, LARS-PETER, WILLMAN, TARMO
Application year: 1994
Main classification: E04B1
IPC codes: E04B1, E04C2